The present invention relates generally to variable power optical lenses, and more particularly to a fluid filled variable power optical lens having a focal length that can be continuously varied to provide focusing capability.
The invention provides a continuously variable power (focal length) lens comprising a generally tubular shaped chamber filled with transparent fluid with a transparent flexible membrane across one opening. As fluid is pumped into or withdrawn from the chamber the elastic membrane bulges outwardly or sags inwardly with predictable curvature in a shape defining a positive or negative optical power surface. The optical power of the lens can be continuously adjusted by selectively varying (increasing or decreasing) the fluid pressure in the chamber.
A variable power lens constructed according to the invention allows focusing of an optical device into which the lens is incorporated without the use of movable mechanical parts and allows continuous adjustment of focal length over a finite range without movable lens elements. The invention may be used in any optical application requiring lens power adjustment or focusing, such as focusing the objective lens of night vision goggles (NVG), or as auto-focusing means for eyeglasses. For example, NVGs presently include objective lenses that require manual focusing by translation of the objective lenses toward or away from the image intensifier tubes to permit viewing of objects at various distances. The device may be used in conjunction with a distance sensor to maintain good image focus as the objective distance changes. Use of a miniature fluid lens of the invention together with a distance sensor and an electromechanical pressure transducer provides an autofocus mechanism that could be retrofit to existing NVGs.
For the purpose of describing the invention and defining the scope thereof, the term "optical" or "optically" shall, in accord with customary usage, be defined herein to include only ultraviolet, visible, near infrared, mid-infrared and far infrared regions of the electromagnetic spectrum lying between about 0.1 to about 1000 microns (see, e.g., Optical Physics, Max Garbuny, Academic Press, N.Y., 1965, pp 1-6), and more specifically to the range of from about 0.2 micron, the approximate lower limit of operation of fine quality quartz lenses (Garbuny, p 280), to about 50 microns, the approximate upper limit of operation of long wavelength transmitting material such as thallium bromide-iodide ionic crystal (Garbuny, p 282).
It is therefore a principal object of the invention to provide a variable power optical lens.
It is another object of the invention to provide a fluid filled variable focal length, variable optical power optical lens.
It is yet another object of the invention to provide a variable power optical lens which may be focused without the use of mechanical translation devices.
It is yet another object of the invention to provide a fluid filled variable power optical lens for retrofitting existing optical devices.
It is yet a further object of the invention to provide a variable power optical lens for use in autofocusing devices.
These and other objects of the invention will become apparent as a detailed description of representative embodiments proceeds.